3D simulation of internal convection in a self-propelled oil droplet whose shape is fixed by a rigid frame

Abstract

Self-propelled oil droplets locomote by internal Marangoni convection, and the phenomena have been widely investigated so far. By attaching an exoskeleton frame to an oil droplet dropped into aqueous solution, Marangoni convection is generated due to the concentration distribution of surfactant at the oil droplet interface, in accordance with the directional shape of the frame to determine the locomoting direction. Since Marangoni convection and surfactant diffusion are non-linear phenomena, it is difficult to theoretically describe the motion of oil droplets. Furthermore, the existence of a frame also gives the complex constraints of boundary conditions. In this study, the SPH (Smoothed Particle Hydrodynamics) method is addressed to perform the three-dimensional simulation of the internal convection and the surfactant diffusion, and the principle of self-propelled oil droplets is examined.